A horizontal belt filter is a device which dewaters, filters, cleans, condenses, and refines a solid-liquid slurry. In general, the device rotates an endless fabric wound around a plurality of rollers under a certain tension, and efficiently separates solid/liquid by a vacuum suction device disposed under a portion in which the fabric runs horizontally.
As physical properties demanded from the fabric for the horizontal belt filter, a sufficient solid-liquid separating property, that is, a capturing property sufficient for obtaining a treated matter on the surface of the fabric, and a water filtering property for obtaining a filtered liquid through the fabric are required. Additionally, a peeling property of the treated matter from the fabric, required in sampling the treated matter on the fabric, a cleaning property for removing a stuck residue, rigidity for supporting the treated matter on the fabric, rigidity or running stability for preventing elongation or deformation by tension, meandering caused by a dimensional change or the like, wear resistance to wear generated by friction with the rollers and the like are required.
In Japanese Patent Application Laid-Open No. 2003-275514, invention concerning the fabric for the horizontal belt filter has been laid open, in which permeability and hanging tension are limited. It is described that the fabric has a sufficient solid-liquid separating property, and rigidity. Preferable examples of a fabric texture include a single-layer or multilayered fabric of plain weave, twill weave, or satin weave. In the examples, it is described that the hanging tension and permeability are set to be constant, and accordingly a solid-liquid separating performance is enhanced. However, needless to say, a sufficient solid-liquid separating property and rigidity cannot be obtained in this case.
To obtain the water filtering property, capturing property, rigidity, cleaning property and the like required for the fabric for the horizontal belt filter, it is insufficient to limit the water filtering property or the hanging tension only, and the fabric texture is important. For example, to sufficiently capture the treated matter on the surface of the fabric, the surface needs to have a dense structure, and the texture needs to be superior in the water filtering property. Additionally, the fabric needs to be structured in such a manner that any residue is not left in meshes in a case where the treated matter on the fabric is scratched off the fabric with a scraper or the like, and the fabric has to be superior in rigidity in order to avoid creases or folds, or satisfy running stability or the like. As described above, the fabric which fully satisfies all performances required for the fabric for the horizontal belt filter has not been realized.